1. Field of the Invention
The present invention relates to a gerotor and bearing system for a backwards whirling mass orbital vibrator. In particular, the present invention is directed to a gerotor and bearing apparatus and method to use a whirling mass orbital vibrator to generate vibrations.
2. Prior Art
Subterranean seismic vibration signals are known to be used in order to allow investigation of the geology surrounding subterranean boreholes. For example, the energy industry is known to utilize downhole vibration signals as a seismic energy source for generating information to evaluate the potential for deposits of oil and gas accumulation and other information. Seismic profiles of the earth may be generated from this information.
Seismic signals can be generated by various devices that may employ vibration which generates a sound wave directly or indirectly through the earth.
The use of downhole mechanical vibrations to increase the mobility of petroleum and gas deposits is also known. Vibrations are believed to decrease fluid interfacial tension as well as capillary forces, thereby allowing hydrocarbons to flow more easily.
Mechanical mechanisms to generate vibrations by spinning a shaft to create rotational energy are also known. For example, see Assignee's patents such as U.S. Pat. No. 5,159,160, U.S. Pat. No. 5,305,405, U.S. Pat. No. 5,210,381 and U.S. Pat. No. 5,515,918. The mechanical means may be provided by rotating a shaft in a selected rotational direction which causes a mass to backwards whirl in a direction opposite to rotational direction. Backwards whirl is defined as the motion of a circle having a diameter (d) whirling within another circle having a diameter (D), which generates a hypocycloid with multiple vibrations per rotation as follows:
  d      D    -    d  
In the past, various types of mechanisms were used to insure a controlled backwards whirling motion. In one example, small, involute gears were utilized. It was important to assure that the mass did not encourage the gears to become misaligned, jump the gear teeth and then grind or destroy the gears over time due to misalignment.
Gerotors are one type of known gearing system. A typical gerotor includes an inner gear and an outer gear section. The gerotor is a system wherein the outer gear set has one more gear tooth or lobe than the inner gear set. In the past, gerotors have been used as fluid pumps and/or as hydraulic motors. In fluid pump applications, a fluid porting mechanism is utilized such that when the inner gear section is rotated in relation to the outer gear section, the fluid is pressurized. As the inner gear set rotates, a volume is created. This motion creates a volume of reduced pressure and fluid is drawn in. In a hydraulic motor application, a porting mechanism is used to force hydraulic fluid between the inner and outer gear sections imparting a rotary motion to the inner gear section.
For example, U.S. Pat. No. 6,336,317 to Holtzapple et al discloses use of a gerotor in an engine.
There remains a need to provide a gerotor and bearing system for a whirling mass orbital vibrator that will transmit vibrational energy.
There remains a need to provide a gerotor and bearing system for a whirling mass orbital vibrator that is efficient and will operate effectively downhole with minimal maintenance.
There also remains a need to provide a continuous drip lubrication system for a whirling mass orbital vibrator having a self contained lubricating system.